1. Field of the Invention
The present invention generally relates to projecting a two-dimensional image in monochrome, gray scale or color and, more particularly, to increasing image brightness and reducing speckle noise, while maintaining low power consumption, high resolution, miniature compact size, quiet operation and minimal vibration.
2. Description of the Related Art
It is generally known to project a two-dimensional image on a screen based on a pair of scan mirrors which oscillate in mutually orthogonal directions to scan a laser beam over a raster pattern. See, for example, U.S. Pat. No. 6,655,597. However, the known image projection systems have limited resolution, typically less than a fourth of video-graphics-array (VGA) quality of 640×480 pixels. The physical size and power consumption of the known projection systems are relatively high, thereby rendering them impractical for use in miniature, hand-held, battery-operated applications. Also, the low scan rates of the scan mirrors generate objectionable noise and vibration during use. Speckle noise, which is caused by the coherent nature of laser light, is an omnipresent problem that detracts from good image quality. In the case of color images formed by laser beams of different wavelengths (colors), some laser sources, for example, red semiconductor single mode lasers have insufficient power to produce a color image of uniform brightness, and other laser sources, for example, green lasers, are not readily available.